Image Credit: (Chemistry World, 2008)

Proteins in Beer Brewing.

I hear about proteins in beer brewing and how important they are to beer making all the time, yet my deepest understanding has always been protein’s role in clarity. I had no idea how important it actually is for nearly all aspects of malting, mashing and fermentation! Let’s dive in together and learn something new.

This is a deep dive. So deep, in fact that I am calling this one The Ultimate Guide. There’s just that much to sift through! In the name of making better beer, let’s push through this one and greatly enhance our knowledge! No pain, no gain.

I have included a glossary of terms I use here for convenience! Don’t hesitate to check it out.

Here’s a closer look at the science behind proteins in brewing beer:

Table of Contents

Introduction to Proteins in Beer Brewing

Various proteins affect all kinds of aspects of your finished beer. When it comes to proteins in beer brewing, everything from mouthfeel, foam stability and clarity to overall quality come into play here. This is because proteins interact with polyphenols, hop compounds and other molecules. In this series, look at the different proteins and the role they play in determining the quality of your beer. But first, let’s focus on proline: a very important part of considering the effects of proteins on beer.

Proline is an amino acid. Amino acids are the building blocks of proteins.

Proline

Proteins that are rich in proline can be more prone to interact with polyphenols which leads to the formation of protein-polyphenol complexes. These complexes often become insoluble and is the primary cause of chill haze. If you haven’t seen chill haze before, it appears when the wort is chilled, and will actually disappear when the fermented beer warms up.

Interestingly, proline is NOT absorbed by yeast during fermentation and results in finished beers having higher levels of proline than any other amino acid!

You can combat chill haze and insoluble protein-polyphenol complexes using enzymes that break down proline-rich proteins. The one I use that is widely available, is Clarity Ferm, made by White Labs.

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Clarity Ferm

A bonus effect of using Clarity Ferm is that a byproduct of breaking down these proline-rich proteins in beer brewing means gluten is reduced to levels below 20 ppm! If you are gluten-intolerant, this would likely make beer drinkable for you. Proline-rich proteins like B-hordeins in barley and gliadins in wheat make them resistant to complete digestion in the gastrointestinal tract, which in some people can trigger immune responses. Not a fun time. However, individuals with Celiac should NOT trust a beer marketed as “gluten reduced” or a homebrew made with Clarity Ferm. Even levels of 20 ppm can have negative effects for these folks.

Before we move on, let’s look at how Clarity Ferm really works:

Clarity Ferm utilizes the enzyme called prolyl endopeptidase. This enzyme cleaves the peptide bonds adjacent to proline into smaller peptides, which reduces their ability to cause chill haze and trigger gluten sensitivities!

A brief look at peptides:

What are they? A peptide is a compound consisting of two or more amino acids, joined in an amide linkage, also known as a peptide bond. Peptides are actually very similar to proteins. The primary difference between peptides and proteins is size. Generally, if a chain has fewer than 50 amino acids, it’s considered a peptide, while larger chains are considered polypeptides, or if they have folded into a 3D shape with the help of amino acids, they would become proteins with very specific purposes. In addition to the same benefits protein provides beer, peptides also provide biological stability through antimicrobial properties and reduction of oxidation through antioxidant properties.

Some common peptides in beer

Antimicrobial: (Sørensen et al., 2008), (Behr et al., 2010)

• Defensins
• Thaumatin-like proteins
• Chitinases
• Ribosome-inactivating proteins
• Histatins
• Hop Derived

Antioxidant: (Zhao et al., 2008), (Leitao et al., 2011)

• Barley Derived
• Glutathione
• Proline-rich
• Hop Derived
• Maillard Reaction Products

Back to Proline

Aside from causing chill haze, proline actually is beneficial for yeast metabolism! Proline serves as a source of nitrogen, even if it is not the preferred source of nitrogen. This has an effect on fermentation kinesthetics and impacts the flavor profile of the brew.

“In their natural habitat, S. cerevisiae cells are found on grapes and in grape must, a nitrogen-poor environment where the most abundant nitrogen source is proline. Although proline is the least-preferred nitrogen source for many laboratory yeast strains and although its utilization results in the slowest growth rates, yeast cells have evolved a regulatory circuit that enables them to use the proline in the environment when preferred nitrogen sources are no longer available.”

(Cooper, 2002)

But what does that actually mean?

Yeast has the ability to adapt so well, S. cerevisiae in particular adapted to use lesser preferred nitrogen sources, particularly proline.

Nitrogen affects a ton of aspects of yeast health. Here are the primary impacts and considerations:

1. Yeast Growth and Reproduction
2. Fermentation Rate
3. Fermentation Byproducts
4. Yeast Assimilable Nitrogen
5. End of Fermentation
6. Stress Response

An excellent way to think about how nitrogen might be involved in fermentation, consider this: Nitrogen greatly affects the correct evolution of fermentation. We are going to take a deeper look at nitrogen and its effects on beer in Part III of this series, so subscribe if you want to dive even further! In part II, we will look at hordeins.

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Conclusion

In this intricate dance, proteins in beer brewing play a pivotal role, choreographing a myriad of processes that determine the final taste, appearance, and mouthfeel of the beer. From the haze that forms when you chill your brew to the frothy foam that graces its surface, proteins are the unsung heroes behind these phenomena. As we’ve scratched the surface with this introduction to the world of proteins, particularly focusing on proline and its interactions, it’s evident that understanding these molecular maestros is crucial for any brewer aiming for perfection.

The journey of understanding proteins in beer brewing is vast and complex, much like the brewing process itself. We’ve explored the significance of hordeins, the role of proline-rich proteins, and even the potential benefits of peptides. Each of these components, from B-hordeins to haze-reducing enzymes, plays a unique role in shaping the beer’s character.

But beyond the science and the intricate details, lies the art of brewing. It’s about balancing these elements, understanding their interactions, and using this knowledge to craft a beer that resonates with its drinker. As we wrap up this deep dive into proteins, remember that while knowledge is power, it’s the application of this knowledge that transforms a good beer into a great one. In the next article in this series, we will dive into hordeins!

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Glossary

1. Amino Acids: Organic compounds that combine to form proteins. They are the building blocks of proteins.
2. Chill Haze: A temporary cloudiness or haziness in beer caused by the presence of certain proteins and polyphenols. It appears when the beer is chilled and disappears when warmed.
3. Clarity Ferm: A product by White Labs that contains an enzyme used to break down proline-rich proteins in beer, reducing chill haze and gluten content.
4. Enzymes: Proteins that act as catalysts within living cells, speeding up chemical reactions.
5. Hordeins: A group of proteins found in barley, which can contribute to the gluten content in beer.
6. Peptides: Compounds consisting of two or more amino acids linked in a chain.
7. Polypeptides: Chains of amino acids linked together by peptide bonds. Polypeptides can range in size, and when they are long enough and fold into specific structures, they become functional proteins. The distinction between a polypeptide and a protein is often based on size and functionality. Generally, chains with fewer than 50 amino acids are considered polypeptides, while larger, more complex chains that have folded into a specific three-dimensional shape and have a specific function are termed proteins.
8. Polyphenols: A group of chemicals found in plants, some of which can interact with proteins in beer to affect its clarity and other properties.
9. Proline: An amino acid that plays a significant role in the structure and function of proteins.
10. Prolyl Endopeptidase: An enzyme that breaks down proline-rich proteins, reducing their ability to cause chill haze and gluten sensitivities.
11. Proteins: Large molecules made up of amino acids that play many critical roles in the body. In the context of beer, they affect various aspects like clarity, foam stability, and mouthfeel.
12. S. cerevisiae: A species of yeast commonly used in brewing.
13. Yeast Assimilable Nitrogen (YAN): The combination of free amino nitrogen (FAN), ammonia, and small peptides that yeast can utilize during fermentation.

References

Arendt, E. K., & Zannini, E. (2013). Cereal grains for the food and beverage industries. Woodhead Publishing.

Bamforth, C. W. (2009). Beer: Tap into the art and science of brewing. Oxford University Press.

Behr, J., & Vogel, R. F. (2010). Mechanisms of hop inhibition include the transmembrane redox reaction. Applied and environmental microbiology, 76(1), 142-149.

Boer, V. M. (2007). Transcriptional responses of Saccharomyces cerevisiae to preferred and nonpreferred nitrogen sources in glucose-limited chemostat cultures. FEMS Yeast Research.

Boulton, C., & Quain, D. (2001). Brewing yeast and fermentation. Blackwell Science Ltd.

Cameron-Mills, V., & Brandt, A. (1988). Expression of a Hordein Gene Family. Plant Molecular Biology, 11(5), 491-502.

Chemistry World. (2008). [Beer brewing process]. Retrieved from https://www.chemistryworld.com/features/trouble-brewing/3004872.article

Cooper, T. G. (2002). Transmitting the signal of excess nitrogen in Saccharomyces cerevisiae from the Tor proteins to the GATA factors: connecting the dots. FEMS Microbiology Reviews, 26(3), 223–238. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC85206/

Mascher, M., Gundlach, H., Himmelbach, A., Beier, S., Twardziok, S. O., Wicker, T., … & Spannagl, M. (2019). A chromosome conformation capture ordered sequence of the barley genome. Nature, 544(7651), 427-433.

Pugh, T., Mauricio, J. C., & Timberlake, C. F. (2000). The impact of nitrogen composition on yeast fermentation, and wine flavour and composition. Proceedings of the Australian Wine Industry Technical Conference (Vol. 10), 76-83.

Shewry, P. R., & Tatham, A. S. (1990). The prolamin storage proteins of cereal seeds: structure and evolution. Biochemical Journal, 267(1), 1-12.

Sørensen, L. K., & Elvig-Jørgensen, S. G. (2008). Antimicrobial peptides from plants. In Proteins in Food Processing (pp. 365-392).